PHP5

To configure a decorator, pass an array of options or a Zend_Config object to its constructor, an array to setOptions(), or a Zend_Config object to setConfig().

Standard options include:

The decorator interface specifies methods for interacting with options. These include:

Decorators are meant to interact with the various Zend_Form class types: Zend_Form, Zend_Form_Element, Zend_Form_DisplayGroup, and all classes deriving from them. The method setElement() allows you to set the object the decorator is currently working with, and getElement() is used to retrieve it.

Each decorator's render() method accepts a string, $content. When the first decorator is called, this string is typically empty, while on subsequent calls it will be populated. Based on the type of decorator and the options passed in, the decorator will either replace this string, prepend the string, or append the string; an optional separator will be used in the latter two situations.

Zend_Form ships with many standard decorators; see the chapter on Standard Decorators for details.

If you find your rendering needs are complex or need heavy customization, you should consider creating a custom decorator.

Decorators need only implement Zend_Decorator_Interface. The interface specifies the following:

<?php
interface Zend_Decorator_Interface
{
    public function __construct($options = null);
    public function setElement($element);
    public function getElement();
    public function setOptions(array $options);
    public function setConfig(Zend_Config $config);
    public function setOption($key, $value);
    public function getOption($key);
    public function getOptions();
    public function removeOption($key);
    public function clearOptions();
    public function render($content);
}
?>

To make this simpler, you can simply extend Zend_Decorator_Abstract, which implements all methods except render().

As an example, let's say you wanted to reduce the number of decorators you use, and build a "composite" decorator that took care of rendering the label, element, any error messages, and description in an HTML div. You might build such a 'Composite' decorator as follows:

<?php class My_Decorator_Composite extends Zend_Form_Decorator_Abstract
{
    public function buildLabel()
    {
        $element = $this->getElement();
        $label = $element->getLabel();
        if ($translator = $element->getTranslator()) {
            $label = $translator->translate($label);
        }
        if ($element->getRequired()) {
            $label .= '*';
        }
        $label .= ':';
        return $element->getView()->formLabel($element->getName(), $label);
    }

    public function buildInput()
    {
        $element = $this->getElement();
        $helper  = $element->helper;
        return $element->getView()->$helper(
            $element->getName(),
            $element->getValue(),
            $element->getAttribs(),
            $element->options
        );
    }

    public function buildErrors()
    {
        $element  = $this->getElement();
        $messages = $element->getMessages();
        if (empty($messages)) {
            return '';
        }
        return '<div class="errors">' . $element->getView()->formErrors($messages) . '</div>';
    }

    public function buildDescription()
    {
        $element = $this->getElement();
        $desc    = $element->getDescription();
        if (empty($messages)) {
            return '';
        }
        return '<div class="description">' . $desc . '</div>';
    }

    public function render($content)
    {
        $element = $this->getElement();
        if (!$element instanceof Zend_Form_Element) {
            return $content;
        }
        if (null === $element->getView()) {
            return $content;
        }

        $separator = $this->getSeparator();
        $placement = $this->getPlacement();
        $label     = $this->buildLabel();
        $input     = $this->buildInput();
        $errors    = $this->buildErrors();
        $desc      = $this->buildDescription();

        $output = '<div class="form element">'
                . $label
                . $input
                . $errors
                . $desc
                . '</div>'

        switch ($placement) {
            case (self::PREPEND):
                return $output . $separator . $content;
            case (self::APPEND):
            default:
                return $content . $separator . $output;
        }
    }
}
?>

You can then place this in the decorator path:

<?php
// for an element:
$element->addPrefixPath('My_Decorator', 'My/Decorator/', 'decorator');

// for all elements:
$form->addElementPrefixPath('My_Decorator', 'My/Decorator/', 'decorator');
?>

You can then specify this decorator as 'Composite' and attach it to an element:

<?php
// Overwrite existing decorators with this single one:
$element->setDecorators(array('Composite'));
?>

While this example showed how to create a decorator that renders complex output from several element properties, you can also create decorators that handle a single aspect of an element; the 'Decorator' and 'Label' decorators are excellent examples of this practice. Doing so allows you to mix and match decorators to achieve complex output -- and also override single aspects of decoration to customize for your needs.

For example, if you wanted to simply display that an error occurred when validating an element, but not display each of the individual validation error messages, you might create your own 'Errors' decorator:

<?php class My_Decorator_Errors
{
    public function render($content = '')
    {
        $output = '<div class="errors">The value you provided was invalid;
            please try again</div>';

        $placement = $this->getPlacement();
        $separator = $this->getSeparator();

        switch ($placement) {
            case 'PREPEND':
                return $output . $separator . $content;
            case 'APPEND':
            default:
                return $content . $separator . $output;
        }
    }
}
?>

In this particular example, because the decorator's final segment, 'Errors', matches the same as Zend_Form_Decorator_Errors, it will be rendered in place of that decorator -- meaning you would not need to change any decorators to modify the output. By naming your decorators after existing standard decorators, you can modify decoration without needing to modify your elements' decorators.